A subsidiary of Alcoa, the multinational aluminium group, has pleaded guilty in the US to a bribery offence relating to the payment of kickbacks to Bahraini officials through an unnamed London-based middleman with close ties to Bahrain's royal family.

The Alcoa admission comes less than six weeks after the surprise collapse of the UK trial of Victor Dahdaleh, a London-based consultant who had been under investigation by the Serious Fraud Office (SFO) for four years in relation to the bribery scandal.

Alcoa also reached a parallel civil settlement with the US Securities and Exchange Commission (SEC) agreeing to pay $161m in disgorgement, bringing the total cost to the New York-listed group to $384m. Alcoa, which has already paid $85m to Bahraini state-run aluminium firm Alba to settle another civil claim, said it "welcomes the resolution of this legacy legal matter".

Dahdaleh, a British-Canadian national, was accused of paying tens of millions of dollars in bribes to former managers of Alba in return for a cut of contracts worth more than $3bn. Last month counsel for the SFO told a judge at Southwark crown court that the agency no longer intended to pursue the prosecution, in part after a star witness, Bruce Hall – accused of receiving bribes while working for Alba over an eight-year period – significantly changed his evidence.

Hall has already pleaded guilty to a UK conspiracy charge and is expected to be sentenced in March.

The SFO does have powers to bring charges against corporate defendants, but did not do so in the case of Alcoa or its subsidiaries. British prosecutors nevertheless co-operated with their US counterparts in helping secure the guilty plea on Thursday from Alcoa World Alumina.

An SFO spokesman said: "We are aware of the announcement and continue to work with the DoJ."

In contrast with the multimillion-dollar fines and settlements secured by the DoJ and SEC, the SFO's aborted prosecution of Dahdaleh has left the businessman open to pursue a substantial claim for costs against taxpayer funds.

The US acting assistant attorney general Mythili Raman thanked the SFO for its help, adding: "Alcoa World Alumina today admits to its involvement in a corrupt international underworld in which a middleman, secretly held offshore bank accounts, and shell companies were used to funnel bribes to government officials in order to secure business.

"The law does not permit companies to avoid responsibility for foreign corruption by outsourcing bribery to their agents, and, as today's prosecution demonstrates, neither will the Department of Justice."